Synthesis and characterization of attosecond light vortices in the extreme ultraviolet

Infrared and visible light beams carrying orbital angular momentum (OAM) are currently thoroughly studied for their extremely broad applicative prospects, among which are quantum information, micromachining and diagnostic tools. Here we extend these prospects, presenting a comprehensive study for the synthesis and full characterization of optical vortices carrying OAM in the extreme ultraviolet (XUV) domain. We confirm the upconversion rules of a femtosecond infrared helically phased beam into its high-order harmonics, showing that each harmonic order carries the total number of OAM units absorbed in the process up to very high orders (57). This allows us to synthesize and characterize helically shaped XUV trains of attosecond pulses. To demonstrate a typical use of these new XUV light beams, we show our ability to generate and control, through photoionization, attosecond electron beams carrying OAM. These breakthroughs pave the route for the study of a series of fundamental phenomena and the development of new ultrafast diagnosis tools using either photonic or electronic vortices

Mechanisms underlying pituitary hypoplasia and failed cell specification in Lhx3-deficient mice

AbstractThe LIM homeodomain transcription factor, LHX3, is essential for pituitary development in mouse and man. Lhx3 engineered null mice have profound pituitary hypoplasia that we find is attributable to an increase in cell death early in pituitary development. Dying cells are localized to regions of TPIT expression indicating that cell death may contribute to the severe reduction in differentiated corticotrope cells and lower expression of the corticotrope transcription factors, TPIT and NEUROD1. Lhx3 deficiency also results in dorsal ectopic expression of transcription factors characteristic of gonadotropes, SF1 and ISL1, but no gonadotropin expression. This apparent disturbance of cell differentiation may be due, in part, to loss of NOTCH2. NOTCH2 is normally expressed in the pituitary at the boundary between dorsal, proliferating cells and ventral, differentiating cells and is important for maintaining dorsal–ventral patterning in other organs. Thus, Lhx3 contributes significantly to pituitary development by maintaining normal dorsal–ventral patterning, cell survival, and normal expression of corticotrope-specific transcription factors, which are necessary for repressing ectopic gonadotrope differentiation

Birthdating studies reshape models for pituitary gland cell specification

AbstractThe intermediate and anterior lobes of the pituitary gland are derived from an invagination of oral ectoderm that forms Rathke's pouch. During gestation proliferating cells are enriched around the pouch lumen, and they appear to delaminate as they exit the cell cycle and differentiate. During late mouse gestation and the postnatal period, anterior lobe progenitors re-enter the cell cycle and expand the populations of specialized, hormone-producing cells. At birth, all cell types are present, and their localization appears stratified based on cell type. We conducted a birth dating study of Rathke's pouch derivatives to determine whether the location of specialized cells at birth is correlated with the timing of cell cycle exit. We find that all of the anterior lobe cell types initiate differentiation concurrently with a peak between e11.5 and e13.5. Differentiation of intermediate lobe melanotropes is delayed relative to anterior lobe cell types. We discovered that specialized cell types are not grouped together based on birth date and are dispersed throughout the anterior lobe. Thus, the apparent stratification of specialized cells at birth is not correlated with cell cycle exit. Thus, the currently popular model of cell specification, dependent upon timing of extrinsic, directional gradients of signaling molecules, needs revision. We propose that signals intrinsic to Rathke's pouch are necessary for cell specification between e11.5 and e13.5 and that cell–cell communication likely plays an important role in regulating this process

Approaching Mechanization of Plant Micropropagation

Investigations of materials and methods for growing plant tissue in a continual-flow, liquid nutrient medium as an alternative to semisolid agar medium have been made. Enhanced growth of plant tissue on microporouspolypropylene membranes floating on a liquid nutrient has been demonstrated. Moreover, in vitro plantlets on the microporous membrane are free from entanglement with the support matrix and readily available to mechanizedhandling. Trained growth of plantlets through polypropylene netting shows potential for mechanization by mass handling (separation, singulation, and transfer) of plant tissue cultures

Production of positronium chloride: A study of the charge exchange reaction between Ps and Cl−^{-}

We present cross sections for the formation of positronium chloride (PsCl) in its ground state from the charge exchange between positronium (Ps) and chloride (Cl$^-$) in the range of 10 meV - 100 eV Ps energy. We have used theoretical models based on the first Born approximation in its three-body formulation. We simulated the collisions between Ps and Cl$^-$ using ab-initio methods at both mean-field and correlated levels extrapolated to the complete basis set limit. We have investigated Ps excited states up to ${n=4}$. The results suggest that the channel Ps(${n=2}$) is of particular interest for the production of PsCl in the ground state, and shows that an accurate treatment of the electronic correlation leads to a significant change in the global shape of the PsCl production cross section with respect to the mean-field level.Comment: 13 Pages, 7 Figures, 3 Table

Chromosomal localization of the zinc finger protein 15, Zfp15 , on Mouse Chromosome 4

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47024/1/335_2004_Article_BF00352424.pd

Mouse chromosome 11

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47006/1/335_2004_Article_BF00360837.pd

All hormone-producing cell types of the pituitary intermediate and anterior lobes derive from prop1-expressing progenitors

Mutations in PROP1, the most common known cause of combined pituitary hormone deficiency in humans, can result in the progressive loss of all hormones of the pituitary anterior lobe. In mice, Prop1 mutations result in the failure to initiate transcription of Pou1f1 (also known as Pit1) and lack somatotropins, lactotropins, and thyrotropins. The basis for this species difference is unknown. We hypothesized that Prop1 is expressed in a progenitor cell that can develop into all anterior lobe cell types, and not just the somatotropes, thyrotropes, and lactotropes, which are collectively known as the PIT1 lineage. To test this idea, we produced a transgenic Prop1-cre mouse line and conducted lineage-tracing experiments of Prop1-expressing cells. The results reveal that all hormone-secreting cell types of both the anterior and intermediate lobes are descended from Prop1-expressing progenitors. The Prop1-cre mice also provide a valuable genetic reagent with a unique spatial and temporal expression for generating tissue-specific gene rearrangements early in pituitary gland development. We also determined that the minimal essential sequences for reliable Prop1 expression lie within 10 kilobases of the mouse gene and demonstrated that human PROP1 can substitute functionally for mouse Prop1. These studies enhance our understanding of the pathophysiology of disease in patients with PROP1 mutations.Fil: Davis, Shannon W.. University of South Carolina; Estados UnidosFil: Keisler, Jessica L.. University of South Carolina; Estados UnidosFil: Pérez Millán, María Inés. University of Michigan; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schade, Vanessa. University of Michigan; Estados UnidosFil: Camper, Sally A.. University of Michigan; Estados Unido

WNT signaling affects gene expression in the ventral diencephalon and pituitary gland growth

We examined the role of WNT signaling in pituitary development by characterizing the pituitary phenotype of three WNT knockout mice and assessing the expression of WNT pathway components. Wnt5a mutants have expanded domains of Fgf10 and bone morphogenetic protein expression in the ventral diencephalon and a reduced domain of LHX3 expression in Rathke's pouch. Wnt4 mutants have mildly reduced cell differentiation, reduced POU1F1 expression, and mild anterior lobe hypoplasia. Wnt4 , Wnt5a double mutants exhibit an additive pituitary phenotype of dysmorphology and mild hypoplasia. Wnt6 mutants have no obvious pituitary phenotype. We surveyed WNT expression and identified transcripts for numerous Wnts , Frizzleds , and downstream pathway members in the pituitary and ventral diencephalon. These findings support the emerging model that WNT signaling affects the pituitary gland via effects on ventral diencephalon signaling, and suggest additional Wnt genes that are worthy of functional studies. Developmental Dynamics 237:1006–1020, 2008. © 2008 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58083/1/21511_ftp.pd